1. Field of the Invention
Aspects of the present invention relates to an electron emission display, and more particularly, to an electron emission display having an improved arrangement and structure of the sub-pixels.
2. Description of the Related Art
Generally, electron emission elements are classified into those using hot cathodes as an electron emission source, and those using cold cathodes as the electron emission source.
There are several types of well known electron emission elements using the cold cathode, a field emission array (FEA) type, a surface conduction emission (SCE) type, a metal-insulator-metal (MIM) type, and a metal-insulator-semiconductor (MIS) type.
The FEA type electron emission element includes an electron emission region, and cathode and gate electrodes functioning as driving electrodes for controlling the electron emission of the electron emission region. The electron emission regions are formed of a material having a relatively lower work function or a relatively large aspect ratio, e.g., a carbon-based material such as carbon nanotubes, graphite, and diamond-like carbon, so as to effectively emit electrons when an electric field is formed around the electron emission regions under a vacuum atmosphere.
The electron emission elements are arrayed on a first substrate to constitute an electron emission unit. The electron emission unit is combined with a light emission unit having phosphor layers, black layers, and an anode electrode which are formed on a surface of a second substrate facing the first substrate, to constitute an electron emission display.
In a conventional FEA type electron emission display, on the first substrate, cathode and gate electrodes are formed in a linear parallel pattern extending in directions to intersect each other at right angles with an insulation layer disposed between them, and electron emission regions are formed at each intersected region of the cathode and gate electrodes. Further, on a surface of the second substrate, one of the red, green, and blue phosphor layers is disposed in response to the respective intersected region of the gate and cathode electrodes.
Each of the intersected regions of the cathode and gate electrodes corresponding to one of the phosphor layers constitutes a sub-pixel, and three sub-pixels including the red, green, and blue phosphor layers constitutes a pixel. In current practice, each of the sub-pixels is rectangular-shaped, and rows of sub-pixels are arranged to extend in the long-axis and short-axis directions of the first substrate.
However, in the structure just described above, an electron beam spread occurs at each of the sub-pixels while the display is being operated, and electrons emitted from a particular sub-pixel may reach a phosphor layer of an adjacent sub-pixel that has a different color, thereby emitting a light of a different color.
In particular, the center region of an electron beam spot reaching the respective phosphor layers is convexly oval-shaped along the long-axis direction (typically the horizontal direction of the display), and the phosphor layers in the structure of the sub-pixels described above are disposed close to each other in the long-axis direction of the first substrate in order to realize high resolution, thereby easily causing emission of light of a different color. This emission of light in a different color reduces color purity, thereby deteriorating display quality.
Meanwhile, in order to solve the problems described above, there have been attempts to minimize the electron beam spread by lowering the driving voltage. However, in this case, the flow of electrons is reduced, thereby lessening the luminance.